Angular: SCSS / SASS compiler produces unwanted whitespaces [duplicate] - css

Question

This question already has answers here:
Sass Nesting for :hover does not work [duplicate]
(2 answers)
Closed 3 years ago.
I have *.scss file in an Angular 7 project.
After compiling it, the compiler adds unwanted whitespace to the css, which leads to wrong results in the UI.
To reproduce the error go to...
https://www.sassmeister.com/
...copy and paste the following code.
$color-background-default: white;
$color-foreground-default: black;
$color-background-disabled: #d3d3d3;
$color-foreground-disabled: #808080;
$color-background-mouseover: #00a7dc;
$color-foreground-mouseover: white;
$color-background-mousedown: #00467F;
$color-foreground-mousedown: white;
.Tab
{
background-color: $color-background-default;
color: $color-foreground-default;
:hover
{
background-color: $color-background-mouseover;
color: $color-foreground-mouseover;
}
:active
{
background-color: $color-background-mousedown;
color: $color-foreground-mousedown;
border-color: $color-background-mousedown;
}
}
In the CSS box of Sassmeister you should see, that there are whitespaces between ".Tab" and "hover" and "active" that look like this:
.Tab {
background-color: white;
color: black;
}
//WHITESPACE AFTER Tab
.Tab :hover {
background-color: #00a7dc;
color: white;
}
//WHITESPACE AFTER Tab
.Tab :active {
background-color: #00467F;
color: white;
border-color: #00467F;
}
Now when I remove the whitespaces between Tab and hover and active it looks like this:
.Tab {
background-color: white;
color: black;
}
//NO WHITESPACE AFTER Tab!
.Tab:hover {
background-color: #00a7dc;
color: white;
}
// NO WHITESPACE AFTER Tab!
.Tab:active {
background-color: #00467F;
color: white;
border-color: #00467F;
}
The second option without whitespaces gives me the correct UI result.
My question: How can I avoid these whitespaces in Angular 7?

Answer 1

The parent selector, &, is a special selector invented by Sass that’s
used in nested selectors to refer to the outer selector. It makes it
possible to re-use the outer selector in more complex ways, like
adding a pseudo-class or adding a selector before the parent.
(from SASS official documentation)
So when you write rules for pseudo-class (before, after, hover, active etc.), to refer to the outer selector (only one level higher), put the ampersand like this:
.link {
color: blue;
&:hover {
color: green;
}
}
So, your SCSS code can be rewritten as:
$color-background-default: white;
$color-foreground-default: black;
$color-background-disabled: #d3d3d3;
$color-foreground-disabled: #808080;
$color-background-mouseover: #00a7dc;
$color-foreground-mouseover: white;
$color-background-mousedown: #00467F;
$color-foreground-mousedown: white;
.Tab
{
background-color: $color-background-default;
color: $color-foreground-default;
&:hover
{
background-color: $color-background-mouseover;
color: $color-foreground-mouseover;
}
&:active
{
background-color: $color-background-mousedown;
color: $color-foreground-mousedown;
border-color: $color-background-mousedown;
}
}

Answer 2

You're looking for the sass ampersand.
.Tab {
:hover {
...
}
}
...should be:
.Tab {
&:hover {
...
}
}
& means: "current selector". You use &:hover to specify
#{currentSelector}:hover.
Without the ampersand, it results into #{currentSelector} :hover and that's the way you want it to work for constructs like
.a {
.b {
...
}
}
... which parses as .a .b {...}.
A more ample explanation here.
Note: the ampersand also allows specifying a prefix to current selector. For example:
.a {
.b {
prop: value;
.c & {
prop: otherValue;
}
}
}
will parse into:
.a .b { prop: value; }
.c .a .b { prop: otherValue; }